他没去参加聚会，因为正在为考试复习。
He didn't go to the party because he was studying for his exam.
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because英 /bɪˈkɒz/|美 /bɪˈkɔz/
was英 /wɒz/|美 /wɑz/
studying英 /ˈstʌdiɪŋ/|美 /ˈstʌdiɪŋ/
解释
用过去进行时 `was studying` 说明缺席聚会的原因，because 引出理由从句。
He didn't go to the party because he was studying for his exam.
用过去进行时 `was studying` 说明缺席聚会的原因，because 引出理由从句。